Certainly, but the borders aren't so obvious to me. Is any language going to last 100 years without changing so much it feels 'nothing like' it's origin point?

Even if it hasn't changed in name, it may have changed in spirit. Some languages that promote themselves under very different names are substantially more similar than other cases where new language versions are dramatically different.

What 'essence' makes it the 'same language'? An interesting problem.